Github user rhtyd commented on the pull request: https://github.com/apache/cloudstack/pull/872#issuecomment-217410505 @jayapalu I've tried the client only one by one, one at a time. To share my environment, I'm on a 192.168.0.0/16 network from where all my clients try to connect to the router IP (192.168.50.12). I've checked and even tried dropping all iptables rules and firewall that may be blocking any connection; tcpdump confirmed that no ports/communication was blocked. In the daemon/messages log, I get following logs every time a client connects and then it fails due to timeout; some relevant lines from the log: remote host is behind NAT no matching CHILD_SA config found received retransmit of request with ID 1,, but no response to retransmit I found that strongswan 5.x is much better at handling NAT traversals, so I tried to upgrade to that version but it still did not work out either. Strongswan 5.x failed with following kind of logs: May 5 22:07:52 r-4-VM charon: 14[IKE] sending NAT-T (RFC 3947) vendor ID May 5 22:07:52 r-4-VM charon: 14[ENC] generating ID_PROT response 0 [ SA V V V ] May 5 22:07:53 r-4-VM charon: 13[IKE] received retransmit of request with ID 0,, retransmitting response May 5 22:07:54 r-4-VM charon: 15[IKE] received retransmit of request with ID 0,, retransmitting response May 5 22:07:57 r-4-VM charon: 04[IKE] received retransmit of request with ID 0,, retransmitting response May 5 22:08:22 r-4-VM charon: 16[JOB] deleting half open IKE_SA after timeout May 5 22:08:22 r-4-VM charon: 16[IKE] IKE_SA (unnamed)[2] state change: CONNECTT ING => DESTROYING
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